Asp.net MVC 3: model is empty in controller?

Question

I have a form in which I need to choose between only a few objects.

So here is what I did:

View model created:

public class EntityChooserModel { public IEnumerable<Entity> AvailableEntities { get; set; } public int SelectedId; } 

I have two actions in the controller, one with [HTTPPost], one without. I have a "SessionUserData", which is the session data associated with data model binding.

  [Authorize] public ActionResult EntityChooser(SessionUserData sessionData) { List<Entity> entities = _userStore.GetRoles(User.Identity.Name).Select(ur => ur.Entity).ToList(); Entity entity = sessionData.IdCurrentEntity != null ? entities.Where(e => e.Id == sessionData.IdCurrentEntity).First() : entities.First(); return View(new EntityChooserModel() { SelectedId = entity.Id, AvailableEntities = entities }); } 

.

  [Authorize] [HttpPost] public ActionResult EntityChooser( EntityChooserModel model, SessionUserData sessionData, String returnUrl) { if (ModelState.IsValid) { Entity entity = _userStore.GetRoles(User.Identity.Name).Select(ur => ur.Entity).Where(e => e.Id == model.SelectedId).First(); sessionData.IdCurrentEntity = entity.Id; RedirectToDefaultPage(returnUrl); } return View(model); } 

And a strongly typed view:

 @model My.Full.Namespace.EntityChooserModel @{ ViewBag.Title = "EntityChooser"; Layout = "~/Views/Shared/_LoginLayout.cshtml"; } <div id="login-wrapper"> <div id="title"> <h1>Login</h1> </div> <div id="login"> @using (Html.BeginForm("EntityChooser", "Auth", FormMethod.Post, new { id = "ChooseFormId" })) { @Html.ValidationSummary(true, "Loggin error") <div> <span>Choose an entity:</span> @Html.DropDownListFor(x => x.SelectedId, new SelectList(Model.AvailableEntities, "Id", "Name")) </div> <p class="right-aligned"> <a href="javascript:document.getElementById('ChooseFormId').submit();" class="adm-button"> <span class="next-btn"><span>Select</span></span></a> </p> <input type="submit" style="display: none" /> } </div> </div> 

The problem is that when I get data in the second model, I have an empty object. The collection is empty and the identifier is set to the default value (0).

What's wrong? I can’t find out what I missed on this one.

This is the first time I am making an mvc form that is not ForModel() , and the first time I should use a dropdown

Answer 1

The only input element that your <form> contains is a single drop-down list that only sends the selected value to the server when POSTED. This explains why your AvailableEntities collection property is empty.

How empty the SelectedId field is is because you defined it as a field , not as a property . By default, the middleware only works with properties. Therefore, if you want this to be filled, you must define it as a property:

 public int SelectedId { get; set; } 

As for the AvailableEntities property, you can populate it from your repository in a POST action using the selected identifier.